Your walking should help, but I am thinking you need to find a better place to lay it out before quilting. Even on the floor would be better than on your bed. If no room there, maybe you could use the tables in your local library conference room, or the tables at your local quilt shop. If it isnt pinned tightly and flat, you will get wrinkles and wavy fabric, even with a walking foot. And if you want to use the basting spray, it is very essential that you have a good flat surface to put it on. Maybe a porch or deck? Put on old sheet down first to keep the quilt fabric clean. It won't ever be firm and flat enough on a bed.